The hypothesis tested in these studies was that prosthetic grafts of specific diameters, biomaterial composition, and lumenal topography have different long term patency rates when used as brachiocephalic to pulmonary artery conduits. The specific aims were to test various types of grafts made from knitted and woven polyester (with and without internal/external velour), microporous expanded polytetrafluroethylene (EPTFE), bovine pericardium or umbilical vein. Fifty-five rhesus monkeys had a left thoracotomy and various grafts (4,5 and 6 mm) with lengths of 2-5 cm inserted between the systemic and pulmonary circulations. There were eight deaths prior to 3 month catheterization. One monkey was unable to be catheterized secondary to poor vessels. Therefore, there were 46 monkeys who underwent 3 month catheterization. Thus far, there have only been 7 monkeys who have undergone catheterization at one year. Serial angiographic hemodynamic and ultrasonic measurements were made. Preliminary data show that dacron velour has a poor patency (40%) at 3 months. Bovine umbilical vein and bovine pericardium have a patency rate of 7l% and 75% at 3 months. EPTFE showed a patency rate of 82% at 3 months. These data suggest that when prosthetic conduits are used for palliation of pulmonary oligemia in infants and young children, the choice of conduit is highly important for long term palliation. Further, prosthetic materials do not provide the long lasting palliation of the native subclavian artery as described in l948 by Blalock and Taussig.,